1. Field of Invention
The present invention relates to an optical communication module, such as an optical transmitter, an optical receiver, and an optical transceiver, and to a manufacturing method thereof. More specifically, the present invention relates to a highly reliable, compact, and inexpensive optical communication module and to a manufacturing method thereof.
2. Description of Related Art
An optical communications system essentially can include a light-emitting element that converts electrical signals to optical signals and a light-receiving element that converts optical signals to electrical signals. The light-emitting element and the light-receiving element are connected to one another by an optical fiber. An optical communication module (connector) is used to optically connect an optical element, such as a light-emitting element or a light-receiving element, to an optical fiber in a way that allows the optical element to be attached and detached and the optical fiber to be inserted and removed.
Most conventional optical transmitter modules include a light-emitting element packaged in a can package. The can package is secured to a printed circuit board and is connected to an external circuit. Input signals that drive the light-emitting element are sent from the external circuit to the light-emitting element via a metal terminal (pin). The light-emitting element is typically optically coupled to an optical fiber via a ball lens. The light emitted by the light-emitting element passes through the ball lens and is directed to the optical fiber, which is positioned using a sleeve in the module.
A conventional optical transmitter module, since it uses a can package that is connected to an external circuit via a metal pin, can be reduced in sized only so far. Moreover, conventional optical transmitter modules tend to be comparatively expensive to manufacture, because they comprise a large number of parts and their manufacture involves a large number of steps. Also adding to their expense is a time-consuming step for aligning these components.
Various methods have been explored to solve these problems. For example, related art discloses an optical communication module having a platform and an optical element, the platform having a through-hole for inserting an optical fiber, and the platform further having an electrically conductive layer formed thereon for facilitating the electrical connection with the optical element or external circuit. The optical communication module described in the related art can be miniaturized, because the platform does not use a can package, and positioning is achieved by the through-hole.
However, in the optical communication module described in the related art, a bump for connecting and securing the optical element has to be formed in the perimeter of the through-hole so that the optical element can be mounted above the through-hole in which the optical fiber is inserted. Consequently, the optical element is large and manufacturing cost is high. Moreover, a ferrule typically is connected to the tip of the optical fiber, to support the fiber and ensure alignment. Since, the diameter of the through-hole is widened to match the diameter of the ferrule, the diameter of the hole sometimes exceeds that of the optical element, thus making it impossible to mount the optical element. This type of optical communication module is a consumable supply and thus further reductions in cost are desirable.
The structure of this optical communication module does not lend itself to the addition of an impedance-matched transmission line, and thus there is a limit to driving in high-frequency bands. Hence, the development of an optical communication module that supports high-speed driving is desirable.